1353 results found for Ideas For Design, displaying items 1 - 20
November 16, 2009 IC Simplifies Support For FIPS 140-2 Level 4 Digital Encryption
Many solutions exist to supply Federal Information Processing Standard (FIPS) Revision 2, Level 1 and Level 2 digital encryption.1 However, Levels 3 and 4 require monitoring of the environment. Level 3 could be implemented with tamper switches, but they can be bypassed with jumpers or a paper clip. More sophisticated switch sensors require some filtering and deglitching. Level 4 requires monitoring of the supply voltages and temperature. For best...
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John R. Ambrose
, et al.
November 16, 2009 Diode Tester Limits Reverse Voltage And Forward Current To Protect Sensitive Junctions
Some diode manufacturers caution against using the diode tester function in ohmmeters because it could exceed the reverse-voltage and forward-current ratings of sensitive diodes. This is especially true in optical devices such as photodiodes and laser diodes. However, the circuit described here performs a simple go/no-go test on these diodes while limiting forward current and reverse voltage to safe levels (...
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Michael Gambuzza
November 16, 2009 Adjustment-Free Fan Controller For Under $1
No frills here—just inexpensive functionality. This circuit activates a cooling fan when the temperature of a target high-power-dissipation device, such as a processor chip, exceeds a predetermined limit. The key element in the design is the Epcos PTC Temperature Limit Sensor (see the datasheet at www.epcos.com/inf/55/db/ptc_03/01900191.pdf), which cost about $0.50....
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Jim Keith
November 5, 2009 Garage Door Opener Parts Form IR Intrusion Detector
While creating an infrared beam intrusion detector system, the need for a beam-focusing method became evident. Parts from a modified Genie garage door Safe-T-Beam system, purchased at the local home improvement store, proved to be perfectly suited to the application. The main reason for choosing the Genie unit is that the IR transmitter and receiver housings each contain a plastic lens inside a short plastic tube molded into the housing. The tube and lens...
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Bert Henscheid
November 5, 2009 Achieve MPPT Control Without Power Calculation
A maximum power point tracking (MPPT) controller circuit is extremely useful in solar photovoltaic systems for boosting power usage efficiency. The traditional MPPT design, though, requires the use of a multiplier to calculate power from source voltage and current measurements. However, it’s possible to build an MPPT controller without this multiplication stage by measuring power on the load rather than using source parameters. If we aren’t in the presence of a...
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Giovanni Romeo
October 22, 2009 Simple Circuit Provides Latching Fault Protection
Most switching power-supply controllers provide non-latching fault protection. Satisfying a requirement for a latchoff response to a fault often requires the addition of excessive and redundant circuitry. For power-supply controllers with an external soft-start pin, however, a simple circuit can be added to convert its non-latching fault protection into one with latched protection. For typical controllers, the startup sequence begins by charging the VDD...
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Brian King
October 22, 2009 Calculator Provides Quick Rectifier Ripple Approximation
The standard practice for calculating the ripple voltage of a simple rectifier circuit with a reservoir capacitor (Fig. 1) is to linearize the problem. A linear approximation of the voltage across the reservoir capacitor (Fig. 2) assumes that the discharge time is equal to the period of the input sine wave, which is only approximately true for...
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Hugo Coolens
October 8, 2009 Protect Current-Sense Amplifiers From Negative Overvoltage
A high-side current-sense amplifier typically amplifies the differential voltage across a sense resistor and provides an output voltage proportional to the current in that resistor. The amplifier rejects the common-mode voltage on which the sense-voltage rides. Such devices, therefore, can be used to detect overcurrent faults in a load or to make system power-management tradeoffs. Most high-side current-sense amplifiers are well suited for situations in which...
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Prashanth Holenarsipur
, et al.
October 8, 2009 Improved Electronic Birthday Candles Provide Better "Blow Out" Simulation
An earlier Idea for Design described LED “candles” that you could blow out just like normal birthday candles (“Electronic Birthday Candles ‘Blow Out’ One At A Time”). A thermistor and heating resistor combination detected air blown over the thermistor. The control circuit incorporated an 8-bit shift register, a quad op amp, and driver transistors, allowing up to eight ...
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Dhananjay V. Gadre
, et al.
October 8, 2009 Turn A Compensated Current Sink Into A Common Emitter (CE) Amplifier
By adding only a few components, you can turn a temperature- and beta-compensated current sink into a common-emitter (CE) amplifier that maintains a stable biased operating point. This architecture is useful for building stable and device-tolerant BJT Class A amplifiers. The circuit in Figure 1 sinks a constant current (ICE3) through Q3’s collector and emitter. This design is balanced so changes in Q3’s...
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Bill Reeve
October 1, 2009 Two Wires Carry Power And Data
At times, designers face a limited amount of wire and/or a limited cost to communicate with a remote device such as a sensor. Many devices allow communication over an ac or dc power line employing an AM or FM modulation scheme. However, they tend to be costly. This design is a simple, low-cost method for sending data across the same wire used to supply power. It’s based on modulating current from a remote device back to a host. A later example...
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Robert M. Hanrahan
October 1, 2009 Two Wires Carry Power And Data: Backstory
This application is as useful today as it was when I described it in the Oct. 1, 1996 issue. The deployment of sensors has increased significantly, resulting in an increased demand for efficient interconnect techniques between sensors and a host system. The use of only two wires often is attractive from both a cost and reliability standpoint. Sensing applications are no different than others—power and size are being driven smaller while faster operation is desirable...
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Robert M. Hanrahan
October 1, 2009 Backstory: Implement A Spark-Gap-Based Design For Low-Cost Energy Harvesting
The idea of using a spark-gap (SG) as the active element of a converter did not come as a sudden illumination. For a long time, I had been looking for an “acceptable” way of using high-voltage, low-current power-supply sources. For me, “acceptable” simply meant technically feasible without exotic technology and sufficiently efficient to be usable. As it was a selfimposed challenge, I had no definite specifications or deadline. When I had first reviewed the...
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Louis Vlemincq
October 1, 2009 Backstory: Full-Wave Active Rectifier Requires No Diodes
When Electronic Design asked me to write about my Idea for Design, first seen in this year’s August 13 issue, it seemed a simple enough task. We’re all familiar with design. Most of us do it in some form or another almost every day. But, ideas? We all have them, but where do they come from? And what is the essence of a good idea? Simplicity? Elegance? Performance, novelty, creativity? Thomas Edison once said that genius is 1% inspiration and 99% perspiration....
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Anthony H. Smith
October 1, 2009 Use Hybrid PMOS-NMOS Active Loads To Cut Substrate Noise In Differential Amplifiers
BY MAKING A RELATIVELY simple change in a differential amplifier stage, designers can significantly reduce the sensitivity to digital switching noise. In mixed-signal ICs, digital switching noise couples through the common substrate into analog circuits, degrading their performance. In CMOS circuits, most substrate noise couples into NMOS transistors through backgate modulation. That is, the substrate acts as a second gate with a transconductance gain...
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Cosmin Iorga
October 1, 2009 Create A Mixed-Mode Precision Rectifier With Second-Generation Current Conveyors
RECTIFIERS PERFORM AN IMPORTANT signal-processing function in many analog circuits. But conventional half-wave, full-wave, or bridge rectifiers employing diodes can’t be used with low-amplitude signals. The circuit described below is a mixed-mode precision rectifier that can handle both low-amplitude voltage and current signals. Many previously described precision rectifiers use voltage op amps, but conventional voltage op amps suffer from a...
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Abhirup Lahiri
October 1, 2009 High Power-Factor LED Driver Converts AC Input To Power Halogen Replacement
HIGH-BRIGHTNESS LEDS ARE AN inexpensive, robust, and green replacement for halogen light bulbs. LEDs offer a much longer lifetime and eliminate the safety hazards of the inert gas, the expense of the UV filter encasement, and the handling sensitivity of halogens. Since halogen bulbs typically are driven with 12 or 24 V due to their excellent efficacy at those voltages, buildings have been wired with 12- and 24-V ac transformers for halogen...
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Keith Szolusha
October 1, 2009 Interface Circuit Allows Users To Control DC Motor's Speed
THE CIRCUIT IN THE figure provides three levels of speed control for a dc motor, using a PC’s parallel port (LPT1). A C++ program performs the control functions by allowing the signals from the PC port to deliver three different voltages to the motor. The system is an interface circuit that connects the motor to the PC using a 4-bit binary counter (a 74LS193), three current- limiting...
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Firas M. Ali Al-Raie
October 1, 2009 Control Current And Voltage Precisely For Regulators, Oscillators, And Amps
THE CURRENT REGULATOR IN Figure 1 boasts a very high current stability of around 1.7% within a temperature range that spans -40°C to 125°C. It can be used in precise current and voltage regulators, oscillators, and amplifiers. For its operation, the device utilizes a unique composition of thermal coefficients of bipolar transistors and Schottky diodes, which efficiently compensate for each ...
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Gregory Mirsky
September 24, 2009 Buck Converter Powers 5-V Circuits From 12-V Solar-Cell Array
The circuit described here is a 12-V dc to 5-V dc (±5%) switched-mode power supply (SMPS). The supply uses a 12-V input from an array of four 3-V dc, 40-mA solar cells connected in series. (The cells are available for $3.75 each from www.Allelectronics.com.) At the array’s maximum output of 12 V dc, its maximum output power is 12 × 40 mA = 480 mW. The supply’s efficiency is 83% ±1%....
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Paul Florian
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